If your oven is cooling down too fast, you should put an insulation on your oven. It is very important for your oven to have this because this prevents the heat from escaping. If your oven doesn't have a proper insulation, the dome will release all the heat and you will not be able to cook. The goal of this is to maximize the amount of time the heat can be stored into it. There are different types of insulation that you can choose from.